**6. Conclusions**

The differential diagnosis between OA and the two forms of NOA, namely NOA-STF and NOA-HH, can be effectively established in most patients based on a standardized male infertility workup. This is the first and critical step in the clinical decision-making process, and it will guide the physician on how to optimally manage these patients, thus providing the couples with an optimal path for parenthood.

A testicular biopsy should be reserved for the cases of doubt, mainly in patients whose history, physical examination, semen analysis, hormonal evaluation, genetic tests, and imaging studies are inconclusive. Histopathology findings will indicate if spermatogenesis is preserved or disrupted, confirming whether azoospermia is obstructive or nonobstructive. Besides providing specimens for a formal histopathology examination, a diagnostic testis biopsy allows for a concomitant fresh examination of one or more extracted specimens; in the presence of viable sperm, cryopreservation should be offered. Alternatively, a formal surgical scrotal exploration may be utilized in cases of doubt, provided the surgeon is prepared to fix an obstruction at the level of epididymis or vas deferens or perform epididymal or testicular sperm retrieval as appropriate. Therefore, these procedures should be carried out at properly equipped facilities.

A coordinated multidisciplinary effort involving reproductive urologists/andrologists, reproductive gynecologists, geneticists, and embryologists is vital to offer infertility patients with azoospermia the best chance of achieving biological parenthood.

**Author Contributions:** Conceptualization, S.C.E.; writing—original draft preparation, D.L.A. and M.C.V.; writing—review and editing, S.C.E.; supervision, S.C.E. All authors have read and agreed to the published version of the manuscript.

**Funding:** Author processing charges were funded by Next Fertility Procrea Lugano, Switzerland.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** The case studies were presented in accordance with the CARE (CAse Reports) guidelines https://www.care-statement.org/ (accessed on 15 May 2021).

**Data Availability Statement:** All data related to this manuscript are provided in the text.

**Acknowledgments:** We thank our patients who consented to sharing their cases.

**Conflicts of Interest:** The authors declare no conflict of interest.
